seq.take不返回元素

Seq.take 不被视为F中序列的终端操作。正如注释中所提到的,序列被延迟地评估,只有被认为是“终端”的操作才会导致序列被迭代。终端操作包括 Seq.iter (如果要对每个元素执行操作)和 Seq.toList (如果您想要每个元素的具体化列表),以及 Seq.exactlyOne .

在F Interactive中,您可能只需评估 it 以查看前几个值。在下面的示例中,镜像您的,评估 它 最后将显示所取的3个值:

open System

let getTheData() =
    seq {
        for n in {0..1000} -> Guid.NewGuid(), n
    } |> Map.ofSeq

getTheData()
|> Seq.take 3;;

it;;
val it : seq<Collections.Generic.KeyValuePair<Guid,int>> =
  seq
    [[001830fe-9ce3-4649-8609-571e4aedb4c7, 791]
       {Key = 001830fe-9ce3-4649-8609-571e4aedb4c7;
        Value = 791;};
     [001bf0a9-5981-4bc0-bcaf-046af7f4866a, 383]
       {Key = 001bf0a9-5981-4bc0-bcaf-046af7f4866a;
        Value = 383;};
     [004b44a7-85d2-4ce5-91bf-49bcc44f03ba, 91]
       {Key = 004b44a7-85d2-4ce5-91bf-49bcc44f03ba;
        Value = 91;}]